Klimahaus Bremerhaven is part science centre, part immersive museum, built around a journey along the 8th meridian through different climate zones. It is popular for good reason: the displays are physical, dramatic, and easier to absorb than a wall of climate data.
Allow several hours, especially with children. The museum can be busy, and the experience is strongest when you move slowly enough to notice the shifts in heat, cold, humidity, landscape, and human adaptation.